The present invention relates to a method for operating a spindle of a two-for-one twister or cabling machine and a two-for-one twister or cabling machine for accomplishing such method.
It is known from German Patent Publication DE 41 21 913 A1 to influence the yarn tension of an inner yarn and an outer yarn on a cording spindle by means of adjusting mechanisms in such a way that the yarns are guided together at the cabling point at the same yarn tension and speed. In this case, the outer yarn is influenced by an outer yarn brake, the braking effect of which is controlled as a function of an inner yarn brake influencing the inner yarn. The outer yarn is introduced centrally into the cording spindle proceeding from the outer yarn brake and exits radially at a rotating storage disc, which is fastened below the twisted yarn plate on the cording spindle. The outer yarn winds round the storage disc here, at least partially, before the yarn is guided over the outer edge of the twisted yarn plate into the free yarn balloon.
The diameter of the storage disc and the twisted yarn plate, the balloon height from the arrangement of a balloon eyelet or a compensation system, which form the upper rotary point of the yarn balloon, the titre and the rotational speed of the spindle are to be mentioned as the variables which substantially influence the shape and the diameter of the free yarn balloon and the optimization of which, matched to one another, requires a very large outlay, which is often avoided. This is disadvantageous in that the balloon shape decisively also determines the energy consumption at each spindle but the influencing possibilities by means of the parameters mentioned are very small. Thus a reduction in the rotational speed of the spindle is accompanied by a loss in productivity. Furthermore, the yarn titre (yarn count) is based on the yarn material to be processed predetermined by the operator of the textile machine. It is only possible to influence the balloon height to a limited extent as components on the textile machine arranged further on in the yarn course limit the design scope.
A device for cabling is known from the generic European Patent Publication EP 1 167 597 B1, on which a storage disc below the twisted yarn plate to control the yarn tension is dispensed with. Instead, the yarn tension is substantially regulated by a pot which co-rotates with the spindle and substantially prevents the formation of a free yarn balloon except for a residual balloon. In this device, the influence of the storage disc compensating the yarn tension to compensate supply fluctuations is missing. Instead, the forced guidance of the yarn balloon takes place by means of the pot. Owing to the pot, the outer yarn rotating round the spindle is limited with respect to its radial extent, so the yarn tension is regulated on the basis of the friction of the outer yarn on the inner wall of the pot and this corresponds to the effect of using a storage disc. The free residual yarn balloon forming above the pot between the edge thereof and the yarn guide eyelet is not suitable to separate the yarn tension before and after the spindle in order to compensate influences in the supply. By using the co-rotating pot which is formed as a balloon limiter and absorbs the radial forces of the outer yarn, the yarn tension of the outer yarn is lower than in the cabling device known from German Patent Publication DE 41 21 913 A1 with a storage disc.
It proves to be disadvantageous in the cabling device known from European Patent Publication EP 1 167 597 B1 that the use of the pot which is subject to not inconsiderable wear owing to the rotating outer yarn, has to also be moved as a rotating mass by the spindle drive. In addition, the air friction of the pot causes additional losses that have to be compensated by the spindle drive. An achievable energy saving, which can be achieved by dispensing with the formation of the free yarn balloon is more than negated thereby.